1. Field of the Invention
The present invention relates to compositions and methods for controlling the growth of microorganisms on a variety of substrates and in aqueous systems. More particularly, the invention relates to a combination of a microbicide with an N-alkyl heterocyclic compound where the N-alkyl heterocyclic compound potentiates the microbicide's microbicidal effect.
2. Background of the Invention
A large variety of commercial, industrial, agricultural, and wood materials or products are subject to microbiological attack or degradation which reduces or destroys their economic value. Examples of such materials or products include surface coatings, lumber, seeds, plants, leather and plastics. The various temperatures at which such materials or products are manufactured, stored, or used as well as their intrinsic characteristics make them susceptible to growth, attack, and degradation by common microorganisms such as algae, fungi, yeasts, and bacteria. These microorganisms may be introduced during a manufacturing or other industrial process, by exposure to air, tanks, pipes, equipment, and humans. They can also be introduced while using a material or product, for example, by multiple openings and reclosures of packages or from stirring or removing material with contaminated objects.
Aqueous systems are also highly subject to microbiological growth, attack, and degradation. These aqueous systems may be fresh, brackish or saltwater systems. Exemplary aqueous systems include, but are not limited to, latexes, surfactants, dispersants, stabilizers, thickeners, adhesives, starches, waxes, proteins, emulsifying agents, cellulose products, metal working fluids, cooling water, waste water, aqueous emulsions, aqueous detergents, coating compositions, paint compositions, and resins formulated in aqueous solutions, emulsions or suspensions. These systems frequently contain relatively large amounts of water and organic material causing them to be environments well-suited for microbiological growth and thus attack and degradation.
Microbiological degradation of aqueous systems may manifest itself as a variety of problems, such as loss of viscosity, gas formation, objectionable odors, decreased pH, emulsion breaking, color change, and gelling. Additionally, microbiological deterioration of aqueous systems can cause fouling of the related water-handling system, which may include cooling towers, pumps, heat exchangers, and pipelines, heating systems, scrubbing systems, and other similar systems.
Another objectionable phenomenon occurring in aqueous systems, particularly in aqueous industrial process fluids, is slime formation. Slime formation can occur in fresh, brackish or salt water systems. Slime consists of matted deposits of microorganisms, fibers and debris. It may be stringy, pasty, rubbery, tapioca-like, or hard, and may have a characteristic undesirable odor that is different from that of the aqueous system in which it formed. The microorganisms involved in its formation are primarily different species of spore-forming and nonspore-forming bacteria, particularly capsulated forms of bacteria which secrete gelatinous substances that envelop or encase the cells. Slime microorganisms also include filamentous bacteria, filamentous fungi of the mold type, yeast, and yeast-like organisms. Slime reduces yields in production and causes plugging, bulking, and other problems in industrial water systems.
Various chemicals known as microbicides have been used to prevent microbiological deterioration of industrial systems, raw materials, and products. Examples of such microbicides include:
Kathon: a two component microbicide mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI). Kathon is a broad spectrum microbicide used in the pulp and paper industry. Kathon is also recommended to control bacteria and fungi in water-based paper coatings and coating components. Kathon is available from Rohm and Haas, Philadelphia Pa. and as Busan.RTM. 1078 from Buckman Laboratories, Memphis Tenn. Busan.RTM. 1078 is contains 1.15% by weight of CMI and 0.35% by weight of MI as active ingredients. CMI and MI have the following chemical structures: ##STR3##
Bronopol: 2-bromo-2-nitropropane-1,3-diol. Bronopol is available as MYACIDE.RTM. from ANGUS Chemical Company, Northbrook Ill. Bronopol is used in water treatment, oil production fluids, waste injection wells, and with pulp and paper. The chemical formula of bronopol is: ##STR4##
IPBC: Iodopropargyl butyl carbamate. IPBC can be obtained from Troy Chemical, Newark, N.J. IPBC is an effective fungicide, particularly in surface coating compositions, such as paint formulations. IPBC is disclosed in U.S. Pat. Nos. 3,923,870 and 5,219,875. IPBC has the following chemical formula: ##STR5##
IPC: Iodopropargyl carbamate. IPC, an effective microbicide in aqueous systems and on numerous substrates, is disclosed in U.S. Pat. Nos. 4,945,109 and 5,328,926. The chemical formula of IPC is: ##STR6##
DBNPA: 2,2-Dibromo-3-nitrilopropionamide. DBNPA is available from Buckman Laboratories, Memphis, Tenn. as the product Busan.RTM. 94. DBNPA is a broad spectrum bactericide having particular use to control slime in the pulp and paper industry. Busan.RTM. 94 contains 20% by weight of DBNPA as its active ingredient. DBNPA has the chemical structure: ##STR7##
Tribromophenol: 2,4,6-Tribromophenol. Tribromophenol is an antifungal agent available from Great Lakes Chemical, West Lafayette, Ind. under the trade name GREAT LAKES PH-73. The chemical formula of tribromophenol is: ##STR8##
BIT: 1,2-benzisothiazoline-3-one. 1,2-Benzisothiazoline-3-one is a biocide useful for a variety of aqueous systems, such as metalworking fluids, paint, adhesives, starch-based-products, cellulose ether solutions, resin and rubber emulsions. 1,2-benzisothiazoline-3-one is available from ICI Specialty Chemicals, Melbourne, Australia as the product Proxel GXL-20, an aqueous solution of dipropylene glycol 20% by weight of 1,2-benzisothiazoline-3-one as the active ingredient. 1,2-Benzisothiazoline-3-one has the following chemical structure: ##STR9##
Despite the existence of such microbicides, industry is constantly seeking more cost-effective technology which offers equal or better protection at lower cost and lower concentration. The concentration of conventional microbicides and the corresponding treatment costs for such use, can be relatively high. Important factors in the search for cost-effective fungicides include the duration of microbicidal effect, the ease of use and the effectiveness of the microbicide per unit weight.